Handle keyboard actions

When the user gives focus to an editable text view such as an EditText
element and the user has a hardware keyboard attached, all
input is handled by the system. If, however, you'd like to intercept
or directly handle the keyboard input yourself, you can do so by implementing callback methods
from the KeyEvent.Callback interface, such as onKeyDown() and onKeyMultiple().

Both the Activity and View class implement the
KeyEvent.Callback interface, so you
should generally override the callback methods in your extension of these classes as
appropriate.

Note: When handling keyboard events with the KeyEvent class and related APIs, you should expect that such keyboard
events come only from a hardware keyboard. You should never rely on receiving key events
for any key on a soft input method (an on-screen keyboard).

Handle single key events

To handle an individual key press, implement onKeyDown() or onKeyUp() as appropriate. Usually, you should
use onKeyUp() if you want to be sure that you receive
only one event. If the user presses and holds the button, then onKeyDown() is called multiple times.

For example, this implementation responds to some keyboard keys to control a game:

Handle modifier keys

To respond to modifier key events such as when a key is combined with Shift or Control, you can
query the KeyEvent that's passed to the callback method. Several methods
provide information about modifier keys such as getModifiers()
and getMetaState(). However, the simplest solution is to check whether
the exact modifier key you care about is being pressed with methods such as
isShiftPressed() and isCtrlPressed().

For example, here's the onKeyDown() implementation
again, with some extra handling for when the Shift key is held down with one of the keys: